1. Field of Invention
This invention relates to a printer-built-in image-sensing apparatus which print-outputs a sensed image on a print medium immediately after image sensing and an electric-consumption control method in the image sensing apparatus.
2. Description of Related Art
Conventionally, to meet needs to obtain a printout of sensed image on the spot, so-called instant cameras which enable such printout, have been proposed in U.S. Pat. Nos. 3,709,122, 3,727,529, 4,000,500, 4,249,811, and 4,212,524 and the like. Further, an instant film and the like used in those instant cameras have been proposed in U.S. Pat. No. 3,707,116.
However, the conventional instant cameras which record sensed images on instant films cannot provide as excellent printouts as still cameras which use silver chloride films in the point of image quality and preservation. Further, when a plurality of printouts are required from the same sensed image, instant cameras cannot perform extra printing. Therefore in such a case, the single printout must be copied, and the obtained copied image(s) is in further degraded image quality.
Further, the conventional instant cameras printout put all the sensed images on the instant films. If undesirable images from failed image sensing or unnecessary images are included in the sensed images, the instant film is wasted. Furthermore, as it is impossible to print only necessary images later, it is inconvenient for users.
To compensate for these drawbacks of instant cameras, a printer-built-in with a printing function has been proposed. This camera stores image information, obtained from image-sensing by a solid-state image sensor such as a CCD sensor, into a memory, at almost the same time as with exposure of a silver chloride film and print-outputs an image at any desired time.
The camera employs a printer such as a melting type thermal-transfer printer, a sublimation type thermal-transfer printer or an ink-jet type printer. Above all, the ink-jet type printer is superior in downsizing, energy-saving, printing speed, running cost and the like, and it is expected as a promising printer for this camera. U.S. Pat. No. 4,074,324 and Japanese Patent Application Laid-Open No. 54-136325 have disclosed this camera with a printing function.
In the printers used in conventional cameras with a printing function, the sublimation-type thermal-transfer printer performs image transfer by vaporizing ink on an ink sheet using the heat of a printhead. In this construction, energy is applied almost at once to all the recording elements (heaters)—of the printhead having a length corresponding to a print width. This requires a very large amount of electricity for printing.
The melting-type thermal-transfer printer performs image transfer by liquefying ink on an ink sheet with the heat of a printhead. In comparison with sublimation-type thermal-transfer printer, electric consumption is smaller. However, as this printer performs printing by repeating print operation of a predetermined width in a print-sheet feeding direction, it takes a long time to print.
The ink-jet printer forms bubbles from liquid ink and discharges ink from nozzles of a print head and uses less electric consumption than that in the above thermal-transfer printers. At this point, the ink-jet printer is promising as a printer for a camera with a printing function.
However, in all of these printers, energy is applied to the print head for printing on a print sheet. Therefore the power source must maintain a stable voltage during printing. on the other hand, if electricity is consumed to execute another function during print operation, the function might not be properly executed due to fluctuation of the voltage of the power source.
The functions that consume much electricity are as follows.
It is known that a strobe light unit applies electric energy to a light-emitting element using a xenon (Xe) tube to emit light and to irradiate an object in a dark environment for image sensing. Generally, the strobe light unit charges a capacitor by using an oscillator or a booster, to 260V or higher from the power source. Otherwise the unit charges a capacitor from about 300V to 360V as a full-charge, from the power source. Then, the capacitor is discharged by a trigger circuit such that the Xe tube emits light within an exposure period of the camera as strobe light emission. As image-sensing operation accompanied by strobe flash/light emission (strobe image sensing) is being completed, the next electric charge is started, and at the completion of electric charge, the next strobe image sensing is ready.
However, if the printer performs print operation during the above electric charge for strobe light emission, the voltage of the power source fluctuates or becomes unstable due to electric consumption for the electric charge. This disturbs proper application of energy to the printhead during print operation, thus causing unprinted dots or density unevenness in a printed image. Further, after strobe image sensing, if print operation is started during charging of the capacitor, electric consumption increases since electricity must be supplied to both the camera and, the printer. Similar to the above case, this may produce poor printouts. If the charging of the capacitor is temporarily stopped, the charging time is prolonged, and the electric charge is not completed until after the print operation has ended. Accordingly the next image sensing cannot be performed immediately.
Cameras having an electronic view finder such as a liquid crystal display (LCD) for determining the composition of an image are known. The electronic view finder displays image information obtained by a solid-state image sensor on an LCD display panel. In this LCD display panel, electric consumption is large since a backlight is employed for a user to see the displayed image easily. The electronic view finder operates even upon feeding a recording medium for recording sensed images. This temporarily increases electric consumption and shortens the life of a battery.